Matrix switch



5 Sheets-Sheet l lNvs-:NToRs ATTORNEY LYNN H. MATTHIAS JEAN R.HUETIGER MATRIX SWITCH L.. H. MATTHIAS ETAL June 14, 1966 med April e, 196s June 14, 1956 l.. H. MATTHIAS ETAL 3,256,393

MATRIX SWI TCH 3 Sheets-Sheet 2 Filed April 9, 1963 SR AE Sl RMVo O TT TTE NU E MH V NHR NN Nm m5 AT TORN EY June 14 1966 L. H. MATTHIAS ETAL 3,256,393

v MATRIX SWITCH Filed April 9, 1965 3 Sheets-Sheet 5 all@ INVENTORS LYNN H. MATTHIAS J EAN R.HUET16ER mmf/'ffm ATTORNEY United States Patent O 3,256,393 MATRIX SWITCH Lynn H. Matthias, Fox Point, and Jean-Robert Huetiger, Milwaukee, Wis., assignors to Allen-Bradley Company, Milwaukee, Wis., a corporation of Wisconsin Filed Apr. 9, 1963, Ser. No. 272,188 Claims. (Cl. 179-2754) The present invention relates to a matrix switch and a magnetic shielding system for a matrix switch wherein a chassis of high magnetic permeability is adapted to remounted therethrough; a first group of channel members of high magnetic permeability is mounted on one side of the chassis and positioned to conform to said rows in the array of sets of contacts; and a `second group of channel members of high magnetic permeability -is mounted on another side of said chassis and positioned to conform to the columns in said array of 'sets of contacts.

Matrix switches utilizing reed switches have become Well known to those working on computers, numerical control devices and communications apparatus generally, for their ruggedness, durability, compactness and current handling capabilities. Generally speaking, such matrix switches consist of an orthogonal system of elongated operating coils with one or more reed switches mounted at each intersection7 or crosspoint, of the coils. A reed switch is a set of contacts made up of a pair of long slender magnetic reeds enclosed in a glass envelope and having their free ends overlapping. Since such reed switches are intended to be actuated only when both operating coils associated with the reed switch are energized, a 'predetermined reed switch or set of reed switches may be actuated only by contemporaneously energizing the operating coils for the column and row of reed switches containing the one to be energized.

However, matrix switches utilizing reed switches are subject to a major deciency in their vulnerability tov cross-talk. That is, when reed switches and groups of coils producing sufficient flux to actuate the switches are assembled into a compact unit, the tendency, upon energization of a row operating coil and a column operating coil, is to actuate, not only the switch or switches at their crosspoint, but also all of the switches in the vicinity of the crosspoint. This problem is much more acute when latched switches are used.

Several solutions have been proposed for that problem. The desired operation of such a matrix switch may be obtained by careful design of the components to function at precise holding and closing currents, but that expedient merely creates an equally difficult, if not more difficult problem of providing uniformly precise operating signals;

Alternatively, elaborate shielding arrangements have been magnetomotive force required to actuate a reed switch at a crosspoint, to the magnetomotive force required at a crosspoint to actuate any reed switch not at the crosspoint. When the switches are not latched, a substantially better ratio is achieved. The practical effect of that ratio is to permit the matrix switch to be operated with a high degree of reliability by a broad range of operating signals, which range may be readily produced in practice. Those 'results are obtained, in large part, by the use of a chassis ceive an array of sets of contacts in rows and columns n ICC made from a material, such as iron, which has good structural characteristics and high magnetic permeability, and by mounting the reed switches through holes in the chassis so that the row operating coils may be mounted on one side of the chassis and the column operating coils may be mountedon the other side of the'chassis. The shielding is completed by placing channel members of a similar, high permeability material over each of the coils and in contact with the chassis to form a discrete, lowreluctance flux path or circuit around each operating coil, while permitting the ends of the reed switches to project through apertures inthe channel members.

Accordingly, it is an object of the present invention to provide a matrix switch capable of reliable operation throughout a broad amplitude range of operating signal.

It is another object of the present invention to provide a reliable matrix switch utilizing reed switches Iand having broad toleration for variations in the amplitude of the operating signal.

It is another object of the present invention to provide a matrix switch havingsuperior magnetic shielding of each of its crosspoints.

It is another object of the present invention to provide a matrix switch utilizing magnetically latched reed switches and having superior reliability and tolerance for variations in the operating signal.

It is` another object of the present invention to provide a compact matrix switch having superior structural strength and durability.

The foregoing .and other objects will appear in the description to follow. In the description, reference is made to the accompanying drawings which form a part hereof and in which there is shown by way of illustration one specific embodiment in which this invention may be practiced. This embodiment will be described in suicient detail to enable those skilled in the art to practice this invention, but it is to be understood that other embodiments of the invention may be used and that structural changes may be made in the embodiments described without departing from the scope of the invention. Consequently, the following detailed description 'is not to be 'taken in a limiting sense; instead, the scope of the present invention isbest defined by the appended claims.

In the drawings:

FIG. 1 is a top plan view of a preferred embodiment of the present invention with portions cut away to disclose underlying structural features,

FIG. 2 is a bottom plan view of the embodiment shown in FIG. 1 with portions eut away to disclose underlying structural features,

FIG. 3 is a view in section taken along the line 3-3 in FIG. 1, and

FIG. 4 is a view in section of a single crosspoint taken along the line 4-4 in FIG. l.

Referring now specifically to the drawings, FIG. 1 is a top plan view of a preferred embodiment of the present invention with portions cu-t away as indicated in FIG. l and as indicated in line 1-1 in FIG. 3. This embodiment of the present invention utilizes a chassis 1, which consists of a structurally rigid plate of a material such as iron, which has high magnetic permeability. Mounted on a top surface 2 of the .chassis 1 are six elongated coils 3, which will hereafter be referred to as the column coils At regular intervals within each of the column coils 3, a set 7 of four reed switches 8 are mounted through apertures 9 (see FIG. 4) in the chassis 1. Each set 7 of four reed switches 8 has its ends enclosed for protection in a terminal block 10 constructed of a suitable insulating material and having four holes 11 therein to accommodate the reed switches 8.

In FIG. 2 a bottom surface 12 of the chassis 1 is shown with ten elongated coils 13 mounted thereon corresponding to the rows of sets 7 of reed switches 8 mounted in the chassis 1, and these coils 13 shall be hereafter referred to as row coils 13. Each of the row coils 13 is enclosed by a row channel member 14 constructed in the same manner as the column channel -members 4 on the top surface 2 of the chassis 1. The row channel members 14 are secured to the bottom surface 12 of the chassis 1 by means of mounting bolts 15 in the mounting holes 16. At regular intervals within the row coils 13, the sets 7 of reed switches 8 extend therethrough, and through apertures 17 and row channel members 14. The ends of the sets 7 of reed switches 8 extending through the row channel members 14 are also enclosed in terminal blocks 10, as are the ends of the reed switches 8 extending through the column channel members 4 on the top surface of the chassis 1.

Referring to the cut away portions in both FIGS. l and 2, it will be seen that the column coils 4 on the top surface 2 of the chassis 1 cross or intersect the row coils 13 on the bottom surface 12 of the chassis 1, forming intersections or crosspoints 18, `and the sets 7 of reed switches 8 are mounted in each of the crosspoints 18. Adjacent the end of the chassis 1 appearing at the right in both FIGS. 1 and 2 are twelve reed-type control switches 19 which pass through the column coils 3 but have no corresponding row coils.

In FIG. 3, a cabinet 20 is shown in section enclosing the entire matrix switch, although the cabinet 20 is omitted in all other figures for the purpose of clarity. The cabinet 20 is a rectangular enclosure made from a material having magnetic shielding properties so that the cabinet 20 not only encloses the switch, protecting it from dirt and damage, it also serves as a magnetic shield for the switch. The switch is mounted in the lcabinet 1 by means of metal tabs 21, which are secured to the bottom surface 12 of thechassis 1 and to the cabinet 20. As will appear most clearly in FIG. 4, each of the sets 7 of reed switches 8 has a pair of latching magnets 22 secured between the reed switches 8 by means of springs 23 which bear against the inside of the channel members 4 and 14, respectively. The permanent latching magnets 22 are made up of permanent ferrite magnets 24 abutting the springs 23 and iron pole pieces 25 between the ferrite magnets 24 and the chassis 1. Each of the reed switches 8 consists of a glass envelope 26 enclosing a pair of slender, magnetic reeds 27 which are embedded in the sealed ends of the glass envelope 26 and which have their free endsoverlapping in the center of the magnet switch 8. Terminals 28 are secured to the ends of the reeds 24 embedded in the ends of the glass envelope 23.

In the structure described above, each of the column channel members 4 provides three sides of a rectangular shaped magnetic circuit about its enclosed column coil 3, and each of the row channel members 14 forms three sides of a rectangular shaped low reluctance magnetic circuit about its enclosed row coil 13, respectively. The fourth side completing the low reluctance magnetic circuits individually formed about each column coil 3 and row coil 13 is provided by the portion of the chassis 1 between the sides of the corresponding channel member 4 or 14 on which its enclosed coil 3 or 13 rests. To provide the best magnetic circuit it is desirable that the channel members 4 and 14 be mounted in good magnetic contact with the chassis 1.

Hence, when a column coil 3 is energized, its flux path will be confined to its associated column channel member chassis 1.

4 and the chassis 1, in preference to a high reluctance path through air outside a column channel member 4. Similarly, when a row coil 13 is energized, its flux path will be confined to its associated row channel member 14 and the In this manner, the flux produced by each column coil 3 and row coil 13 is confined in its eiect to the sets 7 of reed switches 8 included in the respective rows and columns. In addition, the cabinet 20 provides further magnetic shielding for the matrix switch as a whole.

The control switches 19 serve the usual function, well known to the art, of providing that the input signal for the column coils 3 is fed to the proper coil. The embodiment illustrated is designed to receive and store any six digit decimal number, one digit being stored in each column. The signals for the digits come in sequence from a decoder. Hence, it is the function of the control switch 19, after each digit has been read into the matrix switch to step the input to the next empty column coil 3, to prepare the matrix switch to receive the next digit.

As a result of the function of the various elements of the present invention each crosspoint 18 is magnetically isolated from all other crosspoints 18 to provide a hitherto unobtainably low operating ratio of the magnetomotive force required to energize a reed switch 8 at the predetermined crosspoint over the magnetomotive force necessary at the predetermined crosspoint 18 to energize a reed switch 8 not in the predetermined crosspoint 18. The matrix switch described has an operating ratio better than 1:4. This characteristic of the present invention follows upon the achievement of a matrix switch such that when one column coil 3 is energized, the iiux from that column coil 3 is isolated from all other column coils 3 by the column channel members 4 and from all row coils 13 by the chassis 1. Similarly, the liux from one row coil 13 is isolated from all other row coils 13 bythe row channel members 14 and from all column coils 3 by the chassis 1. Since a reed switch 8 cannot be actuated by the energization of only one of the coils 3 or 13 surrounding it, the contemporary energization of any single column coil 3 and row coil 13 can only actuate the reed switch 8 at their crosspoint.

Although the use of a single elongated column coil 3 for each column of sets 7 of reed switches 8 and a single elongated row coil 13 for each row of sets 7 of reed switches 8 is preferable, the structural and shielding functions of the present invention do not depend upon the use of such coils. To the contrary, the advantages of the present invention would not be any the less if a pair of individual coils were placed about each reed switch 8, one on each side of the chassis l, and the coils in columns on one side of the chassis were connected together and the coils in rows on the other side of the chassis 1 were connected together. Similarly, if it were found desirable to do so, two or more reed switches 8 could be placed within one pair of coils. In the same vein, the embodiments descri-bed show column coils and row coils in an orthogonal system, since that is preferred, but it should be apparent that it is the electrical and magnetic circuits that are critical and not necessarily the geometric arrangement of the crosspoints. The angles between the rows and columns could be greater or less than and, in truth, the rows and columns need not be straight lines, provided that whatever their configuration, each reed switch is located relative to two coils as the reed switches 8 are to their associated column coils 3 and row coils 13 in the embodiment described.

The structure described is also readily adaptable to standard commercial production technics, and hence can be produced in large quantities at a minimum cost consistent with high quality. Moreover, it will lbe apparent that should it benecessary to replace any single reed switch 8, terminal block 10, column coil 3, row coil 13 or latching magnet 22, these operations could be performed rapidly without any special tools or equipment. These advances are obtained by the basic support and vperform the function of' the latching magnet.

, v shielding structure of the at, rigid chassis 1 and the self-supporting channel members 4 and 14, which may be .assembled together by conventional means and require no potting or other sealing and supporting material. Also, the structural strength inherent in a heavy metal chassis 1 with rigid channel members 4 and 14 crissv crossing on either side will be perceived from the foregoing drawings and description. The added protection provided to `the comparatively delicate reed switches 8 is also apparent, and what is more, the air gap between the reeds 27 and the chassis 1 and channel members 4 and 14 will be retained even under the severest conditions so that the matrix switch is practically invulnerable to mechanical damage as a result of forces anticipated in normal handling, shipping and operating situations.

While the embodiment shown utilizes latching magnets 22 to hold the reed switches 8 closed, it is also contemplated that one of the reed switches 8 in each set 7 be used to energize a third, holding coil about the set 7 to Also, there are many applications for matrix switches where latching is not desired, and in such applications neither third coils nor magnets 22 are used. While the magnetic circuits created by the structure of the present invention provide remarkable shielding characteristics, they also enhance the operation of lthe reed switches 8. For example, When only a row coil 13 is energized, a magnetic circuit is created through the reed 27 on the underside 12 of the chassis 1, the row channel member 14 and the chassis 1 back to the reed 27, and this tends to force the two reeds 27 in each reed switch 8 in the row away from each other. The same result obtains when only a column coil 3 is energized. However, when both a row coil 13 and a column coil 3 are energized, the magnetic circuit within the switch is through both reeds 27, drawing their. free ends together, and both channel members 14 and 4. The overall result is to create a reed switch 8 which cannot close unless both its column coil 3 and row coil 13 are contemporaneously energized regardless of the power applied to the coils, provided the reed switch 8 is properly shielded from spurious magnetic elds.

Hence, the scope of the present invention is not to be limited to the structure described and illustrated, but is best dened by the following claims.

We claim:

1. In a matrix switch, the combination comprising:

a chassis of high magnetic permeability;

a coordinate array of .sets 'of contacts mounted in apertures through said chassis; a plurality of column coils mounted about said sets of contacts on one side of said chassis;

a plurality of row coils mounted about said sets of contacts on another side of said chassis;

a plurality of channel members having high magnetic permeability and being mounted over said column v coils to form a highly permeable magnetic circuit in conjunction with said chassis surrounding each of said column coils; Y

and a plurality of channel members 'having high magnetic permeability mounted over said row coils to form a high permeable magnetic circuit in conjunction with said chassis surrounding each of said row coils.

2. In a matrix switch, the combination comprising:

a chassis having high magnetic permeability;

an array of reed switches mounted through said'chassis at spaced intervals thereon;

a row coil associated with each of said reed switches mounted on one side of said chassis, and a column coil associated with each of said reed switches mounted on an opposite side of said chassis from said row coil;

a plurality of channel members having high magnetic permeability, one of said channel members being mounted over each of said row coils on one side of said chassis, and another of said channel members lbeing mounted over each of ysaid column coils on said opposite side of the chassis.

3. In a matrix switch, the combination comprising:

a chassis having structural rigidity and high magnetic permeability; an orthogonal system of channel members including one set of parallel channel members mounted on one side of said chassis and another set of parallel channel members mounted on another side of said chassis, each of said channel members having high magnetic permeability;

an elongated coil mounted in each of said channel members so that said elongated coils on one side of said chassis form crosspoints with said elongated coils on another side of said chassis;

at least one reed switch mounted through said chassis and said elongated coils at each crosspoint of said coils;

and latching means adjacent each of said reed switches on each side of said chassis. 4. In a matrix switch, the combination comprising: a chassis having high `magnetic permeability; a lirst group of elongated coils mounted across one face of said chassis; 4

a second group of elongated coils mounted across another face `of said chassis parallel to vand spaced from said first group of elongated coils and forming a system of intersecting coordinates with said rst group of elongated coils;

at least one reed switch mounted through said chassis at each of said intersections formed by said elongated coils;

and a latching means adjacent each of said reed relays on each side of said chassis and including a pole piece of lhigh permeability immediately adjacent said chassis and a permanent magnet immediately adjacent said pole piece.

5. In a latched reed relay, the combination comprising: a chassis plate having high magnetic permeability and having at least one aperture extending through it; at least one reed switch including a pair of yslender magnetic reeds mounted in opposite ends of an er1- velope to extend inward therefrom so that free ends `of said reeds overlap each other, said switch being mounted through said aperture so that said overlapping ends of said reeds are within said aperture in said chassis;

a high permeability pole piece mounted on each side of said chasis adjacent said reed switch;

a magnetic latching source adjacent each of said pole pieces and said reed switch;

at least one operating coil adjacent said reed switch on each side of saidpchassis;

and at least two channel members of high magnetic permeability, one of said channel members being mounted on one side of said chassis and another of said channel members being mounted on an opposite side of said chassis, each of said channel members being so mounted as to be in magnetic contact with said chassis and to pass over and to at least partially enclose between it and said chassis aportion of said reed switch and said operating coil and said pole piece and said magnetic latching source located on the Asame side of said chassis with it.

6. A latched reed relay according to claim 5 wherein said magnetic latching source is a permanent magnet mounted on said pole piece.

7. A latched reed relay according to claim 6 wherein said permanent magnet is a ferrite magnet.

`8. A matrix switch accroding to claim 2 wherein a high permeability pole piece and a magnetic latching source are mounted adjacent each reed switch on each side of said chassis within said channel members and 3,256,393 7 i said channel members have openings through `them to receive ends of Said reed switches.

9. In a magnetic shield system for a matrix switch, the

combination comprising: a

a chassis of high magnetic permeability having a pair 5 of substantially parallel opposite faces and being adapted to receive a plurality of sets of contacts mounted at predetermined positions therethrough;

an orthogonal system of channel members including a group of row channel members mounted on one of said faces of said chassis to dene elongated enclosed spaces therewith, and a group of column chan nel members mounted on another ofsaid faces 0f said chassis forming elongated enclosed spaces therewith, said channel members lbeing so arranged that 15 -said row channel members cross said column channel members at cross points coinciding with said positions in said chassis for receiving said sets of contacts.

10. A combination shield system land chassis for a 20 matrix switch comprising the combination of a structurally rigid chassis of high magnetic permeability adapted to receive a plurality of sets of contacts mounted therethrough in rows and columns; plurality of row channel members having7 structural rigidity and high magnetic permeability mounted on one side of said chassis to enclose an elongated space to receive said rows `of sets of contacts;

plurality of column channel members having structural rigidity and high magnetic permeability mounted on another side of said chassis to enclose an elongated space for receiving said columns of sets of contacts.

References Cited bythe Examiner UNITED STATES PATENTS l/1940 Elmwood et al. 179-2754 4/1958 Nitsch 179-2754 ROBERT H. ROSE, Primary Examiner.

F. N. CARTEN, Assistant Examiner. 

1. IN A MATRIX SWITCH, THE COMBINATION COMPRISING: A CHASSIS OF HIGH MAGNETIC PERMEABILITY; A COORDINATE ARRAY OF SETS OF CONTACTS MOUNTED IN APERTURES THROUGH SAID CHASSIS; A PLURALITY OF COLUMN COILS MOUNTED ABOUT SAID SETS OF CONTACTS ON ONE SIDE OF SAID CHASSIS; A PLURALITY OF ROW COILS MOUNTED ABOUT SAID SETS OF CONTACTS ON ANOTHER SIDE OF SAID CHASSIS; A PLURALITY OF CHANNEL MEMBERS HAVING HIGH MAGNETIC PERMEABILITY AND BEING MOUNTED OVER SAID COLUMN COILS TO FORM A HIGHLY PERMEABLE MAGNETIC CIRCUIT IN CONJUNCTION WITH SAID CHASSIS SURROUNDING EACH OF SAID COLUMNS COILS; AND A PLURALITY OF CHANNEL MEMBERS HAVING HIGH MAGNETIC PERMEABILITY MOUNTED OVER SAID ROW COILS TO FORM A HIGH PERMEABLE MAGNETIC CIRCUIT IN CONJUNCTION WITH SAID CHASSIS SURROUNDING EACH OF SAID ROW COILS. 